what is the best/fastest way to get from da vinci to termini train station? train, cab etc?
Take the Train.
The Leonardo Express train is fastest--- https://www.raileurope.com/european-trains/leonardo-express/how-to-book.html
PS-- its pretty much a toss up, time wise, between a taxi or the Metro from Termini to the Vatican. Metro cheaper
Another choice is to taxi direct to the Vatican and skip going to Termini. I gather from your other post you are trying to get from FCO to the Vatican to meet your group. If that is the case there is no reason to go through Termini
thanks for the advice. the only reason I would go from FCO to termini is if i CANT store my bag. then i have to go to hotel first, drop it off then back to the Vatican which would eat up a lot of time.
I am hoping to find out if I can store my check on bag (suitcase) for the day so I can go straight to Vatican from airport
Sure hope your flight is on time, and all goes smoothly getting through the airport.